Project Summary/Abstract Early emotion understanding, the ability to identify and interpret emotional expressions and reactions, is crucial for healthy social cognitive development, yet the mechanisms behind the development of this skill remain unclear. The Theory of Constructed Emotion has posited that language may be fundamentally important for developing an understanding of emotions, as it may help children to categorize multiple diverse emotional experiences and displays into a single emotion concept. However, the relation between language and emotion understanding remains largely uninvestigated across late infancy and early childhood, a time when both skills are actively developing. Researching this relation in the first three years after birth could provide crucial insights into specifically how emotion understanding develops, as well as whether the Theory of Constructed Emotion accurately explains development of this skill. The current proposal builds on existing research by taking a developmental approach to investigating the role of language in emotion understanding. The proposal will first identify the relation between productive language and emotion understanding in late infancy (Aim 1). Specifically, 15- to 18-month-olds infants will engage in a non-linguistic eye tracking paradigm to measure emotion matching skills, and this will be related to their productive language abilities. Next, the proposal will delineate the relation between children's language input and emotion understanding in their natural environment (Aim 2) using transcripts from 15- to 35-month-olds in the CHILDES database. Finally, this project will explore how changes in the linguistic environment may cause changes in children's emotion understanding (Aim 3). This will be accomplished using a live action emotion categorization assessment with 24- to 35-month- olds, and by experimentally manipulating the language that children are exposed to while they are learning new emotion categories. Aims 1 and 2 will test the possibility that emotion understanding and language are related among age groups where both skills are developing, and whether this relation extends to both naturalistic environments and laboratory tasks. Aim 3 will then build on these results by exploring whether changes in the language that children are exposed to causally influences their emotion understanding. Taken together, the three aims in this proposal utilize a novel combination of eye tracking, corpus analysis, and live action assessments of emotion category learning. Ultimately, results from this proposal may inform theories of social cognitive development and help identify mechanisms of emotion understanding development. Additionally, the results of this proposal may be used to develop and provide more targeted interventions for young children who struggle with emotion understanding, and help them catch up to their peers before emotion understanding skills begin to stabilize.